The Covenant Empire, also referred to as the Covenant was a religious hegemony made up of many alien species that controlled a large portion of the Orion Arm in the Milky Way galaxy. They waged a genocidal campaign against Humanity until they were defeated due to many factors, the most crucial of which was an internal conflict. While the Covenant's leadership was either lost during the Flood infection of High Charity or during the Battle of Installation 00, the Covenant continues to exist even after the conclusion of the war. In exactly what capacity it continues to operate in remains unknown.
By Bungie